A300 American
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Flapping Ailerons On Takeoff A340

Thu Apr 27, 2006 6:11 am

Hello all,

Back in 2003, I was on LAN from Santiago to BUE, we were in LANs A340 and I noticed the ailerons "flapping" up and down just before takeoff. Is this done purposely by the computer or pilot? What purpose does it fill? Ok, thanks in advance for the answer. Take care

A300 American
 
Jamie757
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RE: Flapping Ailerons On Takeoff A340

Thu Apr 27, 2006 6:53 am

I think this check is done by the pilots to ensure that control surfaces are free and able to move. A pilot will be able to elaborate on this.

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DH106
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RE: Flapping Ailerons On Takeoff A340

Thu Apr 27, 2006 6:59 am

Flapping for extra lift cos the A340 needs all it can get ?  Big grin

Just kiddin.  Silly
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Goldenshield
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RE: Flapping Ailerons On Takeoff A340

Thu Apr 27, 2006 7:15 am

Was this done during the takeoff roll, or was this done prior to entering the runway?
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Matt72033
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RE: Flapping Ailerons On Takeoff A340

Thu Apr 27, 2006 7:21 am

Quoting Jamie757 (Reply 1):
I think this check is done by the pilots to ensure that control surfaces are free and able to move. A pilot will be able to elaborate on this.

yep, you'll see every aircraft do there full and free checks sometime after pushing from the gate and getting to the runway, just to make sure theres no jammed control surfaces
 
A300 American
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RE: Flapping Ailerons On Takeoff A340

Sat Apr 29, 2006 4:38 am

Hello All,

Yes, the flapping of the ailerons occured DURING the takeoff role, which is why it caught my attention. Testing of controlled surfaces it definately wasn`t, since this is performed when the aircraft is stationary or taxiing. Anyway, the flapping stopped right before the aircraft rotated.

Quoting DH106 (Reply 2):
Flapping for extra lift cos the A340 needs all it can get ?


Exactly what I was thinking !!!  bigthumbsup 
 
Pihero
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RE: Flapping Ailerons On Takeoff A340

Sat Apr 29, 2006 7:37 am

Quoting A300 American (Reply 5):
Exactly what I was thinking !!!

So why do you ask the question ?
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neilfking
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RE: Flapping Ailerons On Takeoff A340

Sat Apr 29, 2006 9:27 am

Quoting Pihero (Reply 6):
So why do you ask the question ?

Pihero, I think you are annoyed by anti-AB thoughts here and I sympathise with your annoyance as this sort of thing has no place on the Tech/Ops forum.

However, as you are an AB pilot, I would be interested to know your view on the aileron "flapping" during the T/O roll question. Is it something to do with nosewheel inputs translating through to the ailerons, maybe???

Look forward to your reply. Thank you.

Neil
 
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Starlionblue
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RE: Flapping Ailerons On Takeoff A340

Sat Apr 29, 2006 10:00 am

Goodness. 777 ailerons "flap" as well if you count their connection to the spoilers. But I haven't seen it on take-off. Just landing.
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CX Flyboy
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RE: Flapping Ailerons On Takeoff A340

Sat Apr 29, 2006 2:53 pm

I am not an airbus pilot, so really do not know for sure, but I am going to take a wild stab at it, probably to be shot down as rubbish, but still...


...from what I understand, in an Airbus, if you hold the sidestick to say wings level, then the aircraft will do just that. If a gust of wind picks up a wing, or turbulence occurs, the aircraft knows the pilot wants wings level, and will use the control surfaces automatically to compensate, and give the pilot wings level. The pilot does now have to move the sidestick to compensate.
In a Boeing, the pilot has to move the control column to fight unwanted pitch/angle of bank movements.

So, perhaps what you saw was the aircraft compensating for any wobbles caused by an uneven runway and/or gusts of wind trying to pick up a wing when the pilot was commanding wings level?

Any Airbus pilot willing to elaborate or completely shoot down my theory?
 
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CCA
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RE: Flapping Ailerons On Takeoff A340

Sat Apr 29, 2006 5:52 pm

Quoting CX flyboy (Reply 9):
Any Airbus pilot willing to elaborate or completely shoot down my theory?

Good attempt.

Not on the bus anymore, but it's in "Direct law" on the ground so there is no compensating, after lift off Normal law is blended with Direct law until all you have is Normal law.

You end up with Direct law again at 100' AGL when landing.
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mytravel330
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RE: Flapping Ailerons On Takeoff A340

Mon May 08, 2006 4:51 am

From what i can remember airbus aircraft are fitted with a system called aileron lockout,when the flaps are deployed for take off and landing both ailerons droop down to complete the trailing edge and aid lift/drag when this has to be reduced on one side of the aircraft the aileron on that side will raise slightly whilst the other one stays in line, as opposed to the conventional style of opposite deflection, remember that the force of the aircraft travelling down the runway is pretty substantial and it may just be caused by the force of it gaining momentum and is being forced up slightly more as the aircraft gains speed.

I'm sure i will be corrected if i am wrong but they employ this system in conjunction with the spoilers to turn the aircraft in the air as it reduces torsional twisting of the wing and to alleviate having the opposite effect to what you want if both ailerons are deflected to the same degree without spoilers.
 
SlamClick
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RE: Flapping Ailerons On Takeoff A340

Mon May 08, 2006 5:52 am

I think they were signalling a turn.

Or having some kind of spasms.
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2H4
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RE: Flapping Ailerons On Takeoff A340

Mon May 08, 2006 6:07 am




Quoting SlamClick (Reply 12):
I think they were signalling a turn.

Exactly. That's why if you're turning left, the left aileron goes up, and vice-versa with the right.




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VC-10
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RE: Flapping Ailerons On Takeoff A340

Mon May 08, 2006 7:14 am

Quoting Mytravel330 (Reply 11):
From what i can remember airbus aircraft are fitted with a system called aileron lockout

Aileron Lockout is when an a/c (e.g. B747) is fitted with both high speed & low speed ailerons. With the flaps retracted, the low speed ailerons are locked out i.e. locked in the neutral posn.

What you are referring to on the Airbus is Aileron Droop.
 
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LH463
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RE: Flapping Ailerons On Takeoff A340

Wed May 10, 2006 1:43 pm

I think it was probably just a corsswind correction. When applying power for takeoff, pilots will turn the ailerons into the wind for correction. The greater the corsswind, the more aileron deflection there will be. As the aircraft gains speed and lift over the wing, the ailerons become more responsive, less and less aileron deflection is needed. Finally when the aircraft rotates and becomes airborne the aileron deflection should be very slight, or virtually none at all. As the climbout continues the pilots establish a crab to maintain the "imaginary" runway centerline.

My 2 cents,
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LTU932
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RE: Flapping Ailerons On Takeoff A340

Wed May 10, 2006 4:50 pm

Quoting Neilfking (Reply 7):
Is it something to do with nosewheel inputs translating through to the ailerons, maybe???

The nosewheel I believe isn't handled through the sidestick or a yoke. It's controlled through the wheel tiller.

Don't the ailerons move all the time to maintain the aircraft steady, not only on T/O but also in flight? I've seen this video of an SR MD-11 on FL350.com and it clearly showed that the inboard aileron was moving a little bit in flight.
 
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Starlionblue
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RE: Flapping Ailerons On Takeoff A340

Wed May 10, 2006 8:12 pm

Quoting LTU932 (Reply 16):
Quoting Neilfking (Reply 7):
Is it something to do with nosewheel inputs translating through to the ailerons, maybe???

The nosewheel I believe isn't handled through the sidestick or a yoke. It's controlled through the wheel tiller.

The nosewheel is indeed handled through the tiller, but also has limited movement range with pedal input. So if you move the pedals, you get nosewheel and rudder movement (no aileron movement). This nosewheel movement is locked out off the ground and above a certain speed (on certain aircraft).
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zeke
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RE: Flapping Ailerons On Takeoff A340

Thu May 11, 2006 2:01 am

Quoting A300 American (Thread starter):
Back in 2003, I was on LAN from Santiago to BUE, we were in LANs A340 and I noticed the ailerons "flapping" up and down just before takeoff. Is this done purposely by the computer or pilot? What purpose does it fill? Ok, thanks in advance for the answer. Take care

I think it would be a cross wind takeoff, if you apply too much roll input you will have spoiler deployment.
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wing
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RE: Flapping Ailerons On Takeoff A340

Thu May 11, 2006 7:30 am

Flapping ailerons as you described for a crosswind take off it certainly not the correct technic for Airbus flyby wire airplanes.If lateral side stick input is necessary for strong crosswind take off it shouldn't be large enough to cause the spoiler deployment.
The aircraft will tend to turn into the wind and causing increase in drag.And as the airplane lifts off the wing will drop to the side jeopardising an engine or even a wing strike on the runway.

The inside wing will be pressed more to the wheels therefore reducing the tail clearence and its a major problem as the airplane you are flying gets longer(ie A321)
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